This invention relates generally to the field of tumbler type cylinder locks, and more particularly to a class of such locks in which the tumblers are in the form of flat wafers, and have at least one toothed edge thereof cooperating with similar teeth on a side bar which is fixed against movement parallel to the axis of movement of the tumbler in the lock cylinder. Devices of this type are well known in the art, and the invention lies in specific constructional details permitting marketly lower cost of fabrication, simplification of structure and assembly thereof, as well as substantially foolproof operation.
Typical side bar constructions are illustrated in U.S. Pat. No. 1,600,668 of Sept. 21, 1966 to Winning, and U.S. Pat. No. 1,965,889 to Fitzgerald of July 10, 1934. The former patent discloses a side bar construction which is in entirely fixed relation with respect to the cylinder, and the latter patent discloses a side bar which immobilizes the tumblers until the correct key is inserted in the cylinder. The former construction, while simple, has exhibited doubtful reliability, and the latter construction, while more effective, is not easily fabricated. A more recent improvement is disclosed in U.S. Pat. No. 3,722,241 to Sussina, granted Mar. 27, 1973. This patent discloses a construction employing a side bar brought into action when an attempt is made to rotate the lock cylinder in the absence of a key, a common technique employed when picking the lock. This construction offers engagement of relatively few teeth on the side bar, and relies heavily on the provision of resilient means tending to return each tumbler to locked position when a picking tool is disengaged therefrom.